1. Field of the Invention
The present invention relates to a thin plate joining apparatus. Here, the wording "thin plate" means a thin plate material, a plywood, or a veneer as a material for manufacturing a plywood or the like.
2. Description of the Related Art
One type of thin plate jointing method is commonly known as scarf jointing. This method consists of obliquely cutting the joint surfaces of thin plates at a small angle as shown in FIG. 1, and joining the cut surfaces of the thin plates to each other (hereinafter, the wording "scarf cutting" means the oblique cutting of the end surface of a thin plate, and the wording "scarf shape" means the sectional shape thereof). The scarf joining method can be used for joining thin plates such as a thin plate material, a plywood or a veneer by forming joints.
One example of thin plate cutting/joining apparatuses for scarf-cutting thin plates and joining them to each other is disclosed in Examined Japanese Patent Publication No. SHO 59-5402 (Thin Plate Cutting/Joining Apparatus). In this apparatus, the end surfaces of fed thin plates to be joined are cut in scarf shapes by a cutter. The cutter is provided at an intermediate position in the infeed and outfeed direction of the thin plates on the same feed plane, and is moved in reciprocating motion in a perpendicular direction to the feeding direction of the above thin plate. The end surfaces thus cut are coated with an adhesive. Subsequently, the thin plates are moved by a specified distance and carried to a joining position, wherein the scarf-shape end surfaces are made to vertically overlap and are joined to each other. Thus, the thin plates are continuously joined to each other.
The technique of cutting the end surfaces of thin plates in a scarf-shape and joining them to each other, however, has the following disadvantages.
1. In a thin plate joining apparatus with a simple structure wherein thin plates are freely carried in the same plane by a conveyor or the like, since the joining surfaces are formed in scarf shapes, when the thin plates are simply pressed in the carrying direction to obtain a strong joint, they may slip along the scarf surfaces and one thin plate may overlap the other as shown in (a), (b) and (c) of FIG. 1. To avoid this phenomenon, that is, to firmly join the rear end of the preceding thin plate to the front end of the following thin plate, the joining may be performed such that the moving distance from the front end stopping position of the following thin plate to the rear end stopping position of the preceding thin plate is made constant. However, there often occurs overlap due to subtle errors in feeding, stopping and supporting of the thin plates, or a gap between the joining surfaces because of shortage of moving distance. Therefore, since the joining surfaces are not usually in close contact with each other, it is difficult to make the join surfaces accurately meet each other. PA0 2. In the "Thin Plate Cutting/Joining Apparatus" in Examined Japanese Patent Publication No. SHO 59-5402 described above, the joining is performed in the following manner. The preceding thin plate is fixed at the position where it is cut at the rear end. The following thin plate is also cut at the front end and coated with an adhesive thereon, and is moved from the cutting position by a specified distance up to the rear end cutting position of the preceding thin plate. The scarf portions of the two thin plates are then pressed from the upper side to be joined to each other. Accordingly, when the thin plates are cut and joined, the next thin plate cannot be cut, making it impossible to perform the joining of thin plates by mass production. This lowers productivity and, further, requires an apparatus for lifting and lowering the thin plates from the carrying plane, thus complicating the structure of the whole apparatus.